Viñeta de la adolescencia en Buenos Aires 2004 : el lugar de los jóvenes

Fil: De Rosa Alabaster, Enrique. Centro de Estudios y Terapias Cognitivas; Argentina.Las noticias que presentan a los adolescentes como protagonistas de hechos delictivos o luctuosos\nvan ganando espacio en los medios, en ámbitos nacionales e internacionales, en estratos altos,\nmedios o marginales. Problemas de conducta, de alimentación, drogas, alcohol, asesinatos, suicidios\nentre los jóvenes generan incertidumbre e interrogantes entre los mayores: ¿Problema estructural o\ncoyuntural? ¿Falta de contención o sobreprotección? ¿Mayor conciencia social?

Microwave radar imaging of inhomogeneous breast phantoms using circular holography

Circular holography is a novel reconstruction technique for Breast Microwave Radar (BMR) imaging. Compared to current state of the art BMR image formation methods, this reconstruction approach yields spatially accurate images with higher signal to noise ratios and no artifacts. Nevertheless, a preclinical study is required to assess the feasibility of this technique in realistic breast imaging scenarios. In this paper, a series of preliminary results showing the performance of circular holography on preclinical datasets are presented. These datasets were recorded from inhomogeneous breast phantoms that mimic the dielectric properties and the anatomy of the different breast tissues. These phantoms were fabricated using Magnetic Resonance (MR) images a base model to emulate the shape and volumes of dense tissue regions. The reconstructed BMR images show that tumor and fibroglandular tissue responses can be effectively distinguished, suggesting that circular holography can be used as BMR reconstruction approach in clinical scenarios

Reticulated foam as a biomass support medium in the anaerobic digestion of an industrial wastewater.

This work reports the pilot-scale investigation of various anaerobic reactor systems treating a fruit washing wastewater. An open cell reticulated foam was used as a biomass support media (BSM). The foam pads (25 mm cubes) were randomly packed in the 2.5 m- 3 reactor with an unpacked section beneath the bed. Four general operational regimes were evaluated. These were: single and two stage operation, with and without effluent recycle. Performance was monitored throughout each run in terms of maximum COD loading rate and minimum attainable hydraulic retention time. Biomass concentrations, both within the media and freely suspended between the biomass support particles were measured on samples from each operating regime, their acetoclastic activity being determined in a laboratory test. A method was developed to ascertain whether a difference in biomass activity existed between the outside of an individual biomass support particle and at the centre of the particle, using a radioactively labelled substrate. It was concluded that a two stage system without recycle provided the best performance with respect to the the maximum attainable loading rate (11.6 kgCOD.m- 3 .day). This was approximately twice that for any of the other systems tested. The minimum hydraulic retention time corresponding to this loading was approximately 1.0 d. The superior performance of the two stage system without recycle was attributed to the increased acetoclastic populations brought about by the pre-acidified feed and the plug flow removal kinetics exhibited in reactors without recycle. Two stage systems produced higher levels of biomass in the reactor than their single stage counterparts and a large proportion of the total biomass inventory was present as suspended growth in systems without recycle. Tracer studies showed that the actual HRT was much less than that calculated from flow rate and reactor volume, indicating that large areas of the reactor were not accessible to the substrate. Experiments investigating activity gradients in the BSM indicated that a significant difference existed between the acetoclastic activity of biomass at the centre of a colonized particle and that on the surface. It may be concluded that substrate diffusional limitations played an important role in determining the performance of this type of biomass support. Electron microscope examination of BSP fragments gave little information other than the existence of both attached and suspended growth. Most of the bio mass was present as a dense fibrillar network

The Measurement of the Reflection and Transmission Properties of Conducting Fabrics to Milli-Metric Wave Frequencies

There is increasing interest in conducting fabrics and their uses at RF and microwave frequencies. This paper for the first time looks at the reflection and transmission measurements of bobbinet and knitted materials from around 8GHz into the milli-metric frequency range 110GHz, where the material geometry is comparable to the wavelength of the wave. Bobbinet materials were found to behave like lossy dielectrics and may be useful in the construction of thin light-weight screening and absorption planes. While the knitted materials, with very small mesh geometry, gave a reflection coefficient which was comparable to a metal foil

The microwave properties of tissue and other lossy dielectrics

This thesis describes work on the theoretical modelling and experimental measurement of the complex permittivity of dielectrics. The main focus of research has been into the characterisation of permittivity of planar and layered samples within the millimetre wave band. The measurement method is based on the free-space measurement of the transmission and reflection coefficients of samples. A novel analytical method of determining the transmission and reflection coefficients as functions of frequency arising from a generalised structure of planar dielectric layers is also described and validated. The analytical method is based on signal flow techniques. The measurement and analytical techniques have been applied in two main areas: firstly, the acquisition of new data on human skin in the band 57 to 100GHz and secondly, the detection and location of defects in composite materials for which a band of 90 to 100GHz was used. Measurements have been made on the complex permittivity of a single sample of excised human skin fixed in formaldehyde. The experimental results have been corrected to account for the fixing process in formaldehyde and are projected to body temperature. This data is, to the best of the author’s knowledge, the first of its kind to be published. Predicted skin permittivity based on various relaxation models varies widely and only partially fits the measured data. The experimental results have been used to determine the parameters of a Cole-Cole function which gives the best fit to the measured data. The measured skin data has also been used to calculate power deposition in skin exposed to millimetre wave radiation. This work concludes that a skin surface temperature rise of only 0.20C results from a thirty second exposure to signals of 100W/m2. Experimental work with fibreglass composite samples has shown that defects such as delaminations, voids, matrix cracks and improper cure result in resolvable differences in the dielectric properties of the samples at 90 – 100GHz. The measurement technique is particularly sensitive to the detection of cracks and its spatial resolution is 20mm or better. Whilst confirming the general conclusions of previously published work, the specific findings of this study are novel.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

An Assessment of the Model of Concentration Addition for Predicting the Estrogenic Activity of Chemical Mixtures in Wastewater Treatment Works Effluents

The effects of simple mixtures of chemicals, with similar mechanisms of action, can be predicted using the concentration addition model (CA). The ability of this model to predict the estrogenic effects of more complex mixtures such as effluent discharges, however, has yet to be established. Effluents from 43 U.K. wastewater treatment works were analyzed for the presence of the principal estrogenic chemical contaminants, estradiol, estrone, ethinylestradiol, and nonylphenol. The measured concentrations were used to predict the estrogenic activity of each effluent, employing the model of CA, based on the relative potencies of the individual chemicals in an in vitro recombinant yeast estrogen screen (rYES) and a short-term (14-day) in vivo rainbow trout vitellogenin induction assay. Based on the measured concentrations of the four chemicals in the effluents and their relative potencies in each assay, the calculated in vitro and in vivo responses compared well and ranged between 3.5 and 87 ng/L of estradiol equivalents (E2 EQ) for the different effluents. In the rYES, however, the measured E2 EQ concentrations in the effluents ranged between 0.65 and 43 ng E2 EQ/L, and they varied against those predicted by the CA model. Deviations in the estimation of the estrogenic potency of the effluents by the CA model, compared with the measured responses in the rYES, are likely to have resulted from inaccuracies associated with the measurement of the chemicals in the extracts derived from the complex effluents. Such deviations could also result as a consequence of interactions between chemicals present in the extracts that disrupted the activation of the estrogen response elements in the rYES. E2 EQ concentrations derived from the vitellogenic response in fathead minnows exposed to a series of effluent dilutions were highly comparable with the E2 EQ concentrations derived from assessments of the estrogenic potency of these dilutions in the rYES. Together these data support the use of bioassays for determining the estrogenic potency of WwTW effluents, and they highlight the associated problems for modeling approaches that are reliant on measured concentrations of estrogenic chemicals

Recommendations for building out mosquito-transmitted diseases in sub-Saharan Africa: the DELIVER mnemonic

In sub-Saharan Africa, most transmission of mosquito-transmitted diseases, such as malaria or dengue, occurs within or around houses. Preventing mosquito house entry and reducing mosquito production around the home would help reduce the transmission of these diseases. Based on recent research, we make key recommendations for reducing the threat of mosquito-transmitted diseases through changes to the built environment. The mnemonic, DELIVER, recommends the following best practices: (i) Doors should be screened, self-closing and without surrounding gaps; (ii) Eaves, the space between the wall and roof, should be closed or screened; (iii) houses should be Lifted above the ground; (iv) Insecticide-treated nets should be used when sleeping in houses at night; (v) houses should be Ventilated, with at least two large-screened windows to facilitate airflow; (vi) Environmental management should be conducted regularly inside and around the home; and (vii) Roofs should be solid, rather than thatch. DELIVER is a package of interventions to be used in combination for maximum impact. Simple changes to the built environment will reduce exposure to mosquito-transmitted diseases and help keep regions free from these diseases after elimination. This article is part of the theme issue ‘Novel control strategies for mosquito-borne diseases'

Pollution control can help mitigate future climate change impact on European grayling in the UK

Aim: We compare the performance of habitat suitability models using climate data only or climate data together with water chemistry, land cover and predation pressure data to model the distribution of European grayling (Thymallus thymallus). From these models, we (a) investigate the relationship between habitat suitability and genetic diversity; (b) project the distribution of grayling under future climate change; and (c) model the effects of habitat mitigation on future distributions. Location: United Kingdom. Methods: Maxent species distribution modelling was implemented using a Simple model (only climate parameters) or a Full model (climate, water chemistry, land use and predation pressure parameters). Areas of high and low habitat suitability were designated. Associations between habitat suitability and genetic diversity for both neutral and adaptive markers were examined. Distribution under minimal and maximal future climate change scenarios was modelled for 2050, incorporating projections of future flow scenarios obtained from the Centre for Ecology and Hydrology. To examine potential mitigation effects within habitats, models were run with manipulation of orthophosphate, nitrite and copper concentrations. Results: We mapped suitable habitat for grayling in the present and the future. The Full model achieved substantially higher discriminative power than the Simple model. For low suitability habitat, higher levels of inbreeding were observed for adaptive, but not neutral, loci. Future projections predict a significant contraction of highly suitable areas. Under habitat mitigation, modelling suggests that recovery of suitable habitat of up to 10% is possible. Main conclusions: Extending the climate-only model improves estimates of habitat suitability. Significantly higher inbreeding coefficients were found at immune genes, but not neutral markers in low suitability habitat, indicating a possible impact of environmental stress on evolutionary potential. The potential for habitat mitigation to alleviate distributional changes under future climate change is demonstrated, and specific recommendations are made for habitat recovery on a regional basis

Recommendations for building out mosquito-transmitted diseases in sub-Saharan Africa: the DELIVER mnemonic

In sub-Saharan Africa, most transmission of mosquito-transmitted diseases, such as malaria or dengue, occurs within or around houses. Preventing mosquito house entry and reducing mosquito production around the home would help reduce the transmission of these diseases. Based on recent research, we make key recommendations for reducing the threat of mosquito-transmitted diseases through changes to the built environment. The mnemonic, DELIVER, recommends the following best practices: (i) Doors should be screened, self-closing and without surrounding gaps; (ii) Eaves, the space between the wall and roof, should be closed or screened; (iii) houses should be Lifted above the ground; (iv) Insecticide-treated nets should be used when sleeping in houses at night; (v) houses should be Ventilated, with at least two large-screened windows to facilitate airflow; (vi) Environmental management should be conducted regularly inside and around the home; and (vii) Roofs should be solid, rather than thatch. DELIVER is a package of interventions to be used in combination for maximum impact. Simple changes to the built environment will reduce exposure to mosquito-transmitted diseases and help keep regions free from these diseases after elimination